The present invention relates to orthopedic medicine, and more particularly to systems and methods for restricting relative motion between vertebrae.
Unfortunately millions of people experience back pain, and such is not only uncomfortable, but can be particularly debilitating. For example, many people who wish to participate in sports, manual labor, or even sedentary employment are unable to do so because of pains that arise from motion of or pressure on the spinal column. These pains are often caused by traumatic, inflammatory, metabolic, synovial, neoplastic and degenerative disorders of the spine.
In a normal spinal column, intervertebral discs that separate adjacent vertebrae from each other serve to provide stiffness that helps to restrain relative motion of the individual vertebrae in flexion, extension, axial rotation, and lateral bending. However, a damaged disc may provide inadequate stiffness along one or more modes of spinal motion. This inadequate stiffness may result in excessive relative vertebral motion when the spine is under a given load, as when the patient uses the muscles of the back. Such excessive relative motion may cause further damage to the disc, thereby causing back pain and ultimately, requiring replacement of the disc and/or other operations to decompress nerves affected by central, lateral or foraminal stenosis.
Heretofore, some stabilization devices have been proposed to restrict, but not entirely prevent, relative motion between adjacent vertebrae. These devices often contain linear springs that are too long to be easily positioned between adjacent vertebrae. Thus, they are often impossible to implant on motion segments where there is a short pedicle-to-pedicle displacement. Furthermore, known spinal implants typically have components that are either flexible, allowing limited relative motion between adjacent vertebrae, or rigid, providing fusion between vertebrae. Thus, they do not provide for interchangeability between flexible and rigid components. Accordingly, symptoms that would normally indicate stabilization and fusion of adjacent motion segments cannot be adequately treated, and vice versa. In other words, revision of an implant to provide fusion in place of stabilization is typically not feasible. Finally, many devices, when implanted in multiple levels along the spine, do not flexibly follow the natural curvature of the spine. Such devices may therefore cause discomfort, or restrict spinal motion in an unpredictable and unnatural manner.
Therefore, there exists a need for a system and method which corrects the above-noted shortcomings and allows for dynamic vertebral stabilization to restore normal movement and comfort to a patient.